1. Field of the Invention
The embodiments of the invention provide a structure, method, etc. for a fin differential metal oxide semiconductor (MOS) varactor diode.
2. Description of the Related Art
Variable reactor (varactor) diodes are popular devices in analog/mixed signal technologies. Such diodes are components in voltage-controlled oscillator (VCO) and phase-locked loop (PLL) circuits. A figure of merit is quality factor (Q), which is improved by reducing parasitic resistances and capacitances. Commonly these devices are used in differential mode, and Q can be improved by designing the device specifically for this use.
One method of reducing parasitic resistance is to provide separate positive and negative signal anodes with a common cathode, usually with interdigitated planar anodes.
This is formed by interdigitated anode fingers, alternating positive and negative terminals. Parasitic resistance is decreased between positive and negative terminals as signal path through cathode buried layer and sinker contact is eliminated. However, the signal path still includes a lateral component. In other words, resistance is reduced down to and through the cathode and cathode contact, but there is still a significant lateral resistance between anodes.